Process for the production of polyimide and polyamic ester polymers

ABSTRACT

This disclosure relates to a process of purifying a polymer. The process includes (a) providing an organic solution containing a polyimide or polyamic ester in at least one polar, aprotic polymerization solvent; (b) adding at least one purification solvent to the organic solution to form a diluted organic solution, the at least one purification solvent is less polar than the at least one polymerization solvent and has a lower water solubility than the at least one polymerization solvent at 25° C.; (c) washing the diluted organic solution with water or an aqueous solution to obtain a washed organic solution; and (d) removing at least a portion of the at least one purification solvent in the washed organic solution to obtain a solution containing a purified polyimide or polyamic ester. This disclosure also relates to a process of preparing a film on a semiconductor substrate, as well as related purified polymer solutions, films, and articles.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to U.S. Provisional ApplicationSer. No. 61/824,529, filed on May 17, 2013, the contents of which arehereby incorporated by reference in its entirety.

BACKGROUND

Polyimide polymers have been used for several decades as thermally andchemically resistant materials in a variety of applications. Inaddition, they have superior mechanical properties which make themvaluable for the manufacturing of various electronic devices.

Polyimide (PI) polymers are typically prepared by chemical or thermaltreatment of their precursors, polyamic acid (PAA) polymers or polyamicester (PAE) polymers. While most PAA and PAE polymers are soluble in thepolar, aprotic polymerization solvents in which they are synthesized,the resulting PI polymers formed upon imidization are usually insoluble.In many applications, since the PI polymer is not soluble, the PAA orPAE polymer is coated onto a substrate and cured to temperatures inexcess of 350° C. to form the PI polymer. In recent advancedapplications, coating of a soluble PI polymer is more preferable thancoating of its PAA or PAE precursors because of lower required curingtemperature and lower film thickness loss due to curing, which resultsin less stress on the substrate.

In those cases where the PI polymer remains soluble, isolation andpurification are accomplished by addition of the polymerization solutionto a large amount of a non-solvent. See for example U.S. Pat. No.3,856,752, U.S. Pat. No. 4,026,876, U.S. Pat. No. 5,252,534, U.S. Pat.No. 5,478,915, US20040265731 and US20040235992 which are incorporated byreference. Typical non-solvents are water, low boiling alcohols, such asmethanol and 2-propanol, or hydrocarbon solvents such as hexane ortoluene. The precipitated polymer is then filtered, washed with anadditional large amount of non-solvent and dried under vacuum atelevated temperature. In most cases, in order to obtain a material ofsufficient purity, the polymer must be re-dissolved in a solvent andprecipitated a second time into a non-solvent. Presence of impurities inPI polymers results in compositions with inferior properties such asmechanical, electrical or chemical resistance. In addition, presence ofminute amount of undesired polar aprotic polymerization solvents in thefinal polymer or compositions from those polymers is undesirable fromenvironmental, safety and health perspective. These methods are alsoused to isolate PAA and PAE polymers. In this way, conventionalprocesses used to produce PI, PAA and PAE polymers will often generatefrom 100 kilograms to 500 kilograms of waste for every 1 kilogram ofpolymer produced. Additionally, using conventional methods, it isexceedingly difficult to reduce the amount of residual solvent to adesired level (e.g., less than 1 wt %) due at least in part to thestrong association of the undesired polar aprotic polymerization solventwith the PI, PAA and PAE polymers. Moreover, the excessive amount ofpolymer handling resulting from multiple precipitations, filtrations anddrying steps can further compromise the purity of the polymers fromcontamination with species such as trace metals.

SUMMARY

This disclosure describes an environmentally-friendly, efficient processfor the preparation and purification of soluble polyimide (PI) andpolyamic ester (PAE) polymers. This process can significantly reduce theamount of impurities (e.g., residual solvents or metals) in the PI andPAE polymers obtained while significantly reducing the waste generatedcompared to a conventional precipitation process. The PI and PAEpolymers thus obtained have a wide variety of applications such asdielectric and packaging materials for semiconductor devices.

In one aspect, this disclosure features a process of purifying a polymerthat includes (a) providing an organic solution containing a polyimideor polyamic ester in at least one polar, aprotic polymerization solvent;(b) adding at least one purification solvent to the organic solution toform a diluted organic solution, the at least one purification solventis less polar than the at least one polymerization solvent and has alower water solubility than the at least one polymerization solvent at25° C.; (c) washing the diluted organic solution with water or anaqueous solution to obtain a washed organic solution; and (d) removingat least a portion of the at least one purification solvent in thewashed organic solution to obtain a solution containing a purifiedpolyimide or polyamic ester.

In another aspect, this disclosure features a purified polymer solutionobtained by the above process.

In another aspect, this disclosure features a process of preparing afilm on a substrate that includes (a) providing an organic solutioncontaining a polyimide or polyamic ester in at least one polar, aproticpolymerization solvent; (b) adding at least one purification solvent tothe organic solution to form a diluted organic solution, the at leastone purification solvent is less polar than the at least onepolymerization solvent and has a lower water solubility than the atleast one polymerization solvent at 25° C.; (c) washing the dilutedorganic solution with water or an aqueous solution to obtain a washedorganic solution; (d) removing at least a portion of the at least onepurification solvent in the washed organic solution to obtain a solutioncontaining a purified polyimide or polyamic ester; and (e) coating thesolution containing a purified polyimide or polyamic ester on asubstrate to form a film.

In another aspect, this disclosure features a free-standing filmobtained by the process described above.

In still another aspect, this disclosure features an article containinga semiconductor substrate and a film prepared by the process describedabove on the semiconductor.

BRIEF DESCRIPTION OF DRAWING

FIG. 1 is a graph showing overlay of GPC chromatograms obtained from thepolymer in Example 7 and the polymer in Comparative Example 1.Chromatogram 1 was obtained from the polymer in Example 7. Chromatogram2 was obtained from the polymer in Comparative Example 1.

DETAILED DESCRIPTION

Wherever the term “solvent(s)” is used, if not specifically stated, itrefers to either a single organic solvent or a combination of two ormore organic solvents.

The current disclosure describes an efficient, environmentally-friendlyprocess for the production of PI and PAE polymers having enhancedpurity. In some embodiments, the process described in the currentdisclosure can avoid precipitation and isolation of the solid polymers,and can result in a purified solution of the desired polymer useful forincorporation into compositions of various types, including thermally-and photochemically-curable compositions.

In some embodiments, this disclosure relates to a process of purifying apolymer. The process can include (a) providing an organic solutioncontaining a polyimide or polyamic ester in at least one polar, aproticpolymerization solvent; (b) adding at least one purification solvent tothe organic solution to form a diluted organic solution, the at leastone purification solvent is less polar than the at least onepolymerization solvent and has a lower water solubility than the atleast one polymerization solvent at 25° C.; (c) washing the dilutedorganic solution with water or an aqueous solution to obtain a washedorganic solution; (d) removing at least a portion of the at least onepurification solvent in the washed organic solution to obtain a solutioncontaining a purified polyimide or polyamic ester.

Step 1—Process for Forming a Polyimide or Polyamic Ester

In some embodiments, the step of providing an organic solutioncontaining a polyimide or polyamic ester in at least one polar, aproticpolymerization solvent can be performed by forming a polyimide orpolyamic ester using appropriate starting reagents in at least onepolar, aprotic polymerization solvent without isolating the polyimide orpolyamic ester thus obtained.

For example, in the initial step of one embodiment of the process, oneor more diamine(s) are combined with one or more tetracarboxylic aciddianhydride(s) in at least one (e.g., two, three, or more)polymerization solvent(s) to form a polyamic acid (PAA) polymer. In oneembodiment, the PAA polymer formed is imidized, either chemically orthermally, to form a PI polymer which remains soluble in thepolymerization solvent(s). In another embodiment, the PAA polymer isend-capped by use of an appropriate reagent during the polymer synthesisor by using an appropriate agent after the polymer synthesis and priorto imidization. In another embodiment, the PAA polymer formed isesterified to form a PAE polymer which remains soluble in thepolymerization solvent(s). Alternatively, in another embodiment, the PAEpolymer is formed by combination of a tetracarboxylic half ester withone or more diamines in at least one polymerization solvent(s). Inanother embodiment, the PAE polymer is end-capped by using anappropriate agent prior to imidization.

In one embodiment of this disclosure, a chemical imidizing agent (e.g.,a dehydrating agent) is added to a PAA polymer that catalyzes thering-closing dehydration process of the polyamic acid groups to formimide functionalities, thereby forming a PI polymer. Examples ofsuitable dehydrating agents include, but are not limited to,trifluoromethane sulfonic acid, methanesulfonic acid, p-toluenesulfonicacid, ethanesulfonic acid, butanesulfonic acid, perfluorobutanesulfonicacid, acetic anhydride, propionic anhydride, and butyric anhydride. Inaddition, this dehydration process can be catalyzed by further additionof a basic catalyst. Examples of suitable basic catalysts include, butare not limited to, pyridine, triethylamine, tripropylamine,tributylamine, dicyclohexylmethylamine, 2,6-lutidine, 3,5-lutidine,picoline, 4-dimethylaminopyridine (DMAP) and the like. If used, thebasic catalyst employed can be the same as or different from the basiccatalyst employed in the end-capping reaction described above.

In some embodiments, the PI polymers of this disclosure remain solublein the polymerization solvent(s) following imidization. In someembodiments, the PAE polymers of this disclosure remain soluble in thepolymerization solvent(s) following esterification and/orpolymerization.

Methods to synthesize endcapped and non-endcapped PAA, PI and PAEpolymers are well known to those skilled in the art. Examples of suchmethods are disclosed in U.S. Pat. No. 2,731,447, U.S. Pat. No.3,435,002, U.S. Pat. No. 3,856,752, U.S. Pat. No. 3,983,092, U.S. Pat.No. 4,026,876, U.S. Pat. No. 4,040,831, U.S. Pat. No. 4,579,809, U.S.Pat. No. 4,629,777, U.S. Pat. No. 4,656,116, U.S. Pat. No. 4,960,860,U.S. Pat. No. 4,985,529, U.S. Pat. No. 5,006,611, U.S. Pat. No.5,122,436, U.S. Pat. No. 5,252,534, U.S. Pat. No. 5,478,915, U.S. Pat.No. 5,773,559, U.S. Pat. No. 5,783,656, and U.S. Pat. No. 5,969,055, USpatent applications US20040265731, US20040235992, and US2007083016, andEuropean patent application EP0317754 A2, the contents of which arehereby incorporated by reference.

The polymerization solvent(s) is generally one or a combination of twoor more polar, aprotic solvents. Suitable polar, aprotic solventsinclude, but are not limited to, dimethylformamide (DMF),dimethylacetamide (DMAc), N-formylmorpholine (NFM),N-methylpyrrolidinone (NMP), N-ethylpyrrolidinone (NEP),dimethylsulfoxide (DMSO), gamma-butyrolactone (GBL), hexamethylphosphoric acid triamide (HMPT), tetrahydrofuran (THF),methyltetrahydrofuran, 1,4-dioxane and mixtures thereof.

In another embodiment, the reaction mixture for the polymerization,imidization, and/or esterification reaction can also include anadditional polymerization co-solvent. Examples of suitablepolymerization co-solvents include, but are not limited to1,2-dimethoxyethane, 1,2-dimethoxypropane, diglyme, triglyme, andtetraglyme. In some embodiments, the polymerization solvents and/or thereaction co-solvents can be water miscible solvents.

Examples of suitable diamines that can be used to prepare a PI or PAEpolymer include, but are not limited to,4,4′-[1,4-phenylene-bis(1-methylethylidene)]bisaniline (DAPI),2,2-bis(4-[4-aminophenoxy]phenyl)propane (BAPP),2,2-bis(4-[4-aminophenoxy]phenyl)hexafluoropropane (HFBAPP),2,2-bis(4-aminophenyl)hexafluoropropane (Bis-A-AF), 4,4′-oxydianiline(ODA), 1,3-phenylene diamine, 1,4-phenylene diamine,4,4′-methylenedianiline (MDA), 3,4′-oxydianiline,4,4′-diaminodiphenylsulfone (DDS), 3,3′-diaminodiphenylsulfone,4,4′-diaminodiphenylsulfide (ASD), 1,3-bis(3-aminophenoxy)benzene(APB-133), 4,4′-methylene-bis(2-chloroaniline),1,3-bis(aminopropyl)tetramethyldisiloxane, m-tolidine, o-toluidine,1,4-diaminodurene (DAD), 1,3-diaminomesitylene (DAM) and the diaminesmentioned in the US patents and US patent applications referenced above.

Examples of suitable tetracarboxylic acid dianhydrides that can be usedto prepare a PI or PAE polymer include, but are not limited to,pyromellitic dianhydride (PMDA), 3,3′,4,4′-benzophenone tetracarboxylicdianhydride (BTDA), 2,2′-bis(3,4-dicarboxyphenyl)hexafluoropropanedianhydride (6FDA), 3,3′,4,4′-biphenyl tetracarboxylic dianhydride(BPDA), 4,4′-oxydiphthalic anhydride (ODPA),5-(2,5-dioxotetrahydrol)-3-methyl-3-cyclohexene-1,2-dicarboxylicanhydride (B-4400), 4,4′-bisphenol A dianhydride (BPADA),3,3′,4,4′-diphenylsulfone tetracarboxylic dianhydride (DSDA) ethyleneglycol bis(trimelllitic anhydride) and the tetracarboxylic aciddianhydrides mentioned in the US patents and US patent applicationsreferenced above.

A range of different time, temperature and concentration conditions forthe polymerization, imidization and esterification reactions may besuitably employed. Examples of such processes are described in the USpatents and US patent applications referenced above. One skilled in theart will understand appropriate conditions to employ for thesesyntheses.

Step 2—Dilution with Purification Solvent(s)

After the polymerization, imidization, and/or esterification reaction instep 1, the reaction mixture formed in step 1 can be diluted with atleast one (e.g., two, three, or more) purification solvent(s) to form adiluted organic solution containing the polyimide or polyamic ester. Thepurification solvent(s) can be a solvent or combination of two or moresolvents which is less polar than the polar, aprotic polymerizationsolvent(s) and has lower solubility in water than the polymerizationsolvent(s) employed at 25° C. Without wishing to be bound by theory, itis believed that the two key functions of the purification solvent(s)are to (1) maintain the PI or PAE polymer in solution and (2) form abiphasic mixture with water and/or an aqueous solution containing anadditive. In the context of this disclosure, biphasic mixture refers toa mixture containing two distinct and separate phases (e.g., twodistinct liquid phases).

In some embodiments, the purification solvent(s) can include an ester,an ether, a ketone, a hydrocarbon optionally substituted by at least onehalide (e.g., F, Cl, Br, or I), or a mixture thereof. Examples ofsuitable purification solvent(s) include, but are not limited to, methylacetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butylacetate, isobutyl acetate, sec-butyl acetate, cyclohexyl acetate, ethyllactate, propylene glycol monomethyl ether acetate (PGMEA),tetrahydrofurfuryl acetate, propyl formate, butyl formate, isobutylformate, pentyl formate, epsilon-caprolactone, diethyl ether, dipropylether, dibutyl ether, dicyclohexyl ether, cyclopentyl methyl ether,methyl tert-butyl ether, ethyl tert-butyl ether, anisole, phenyl ethylether, diphenyl ether, 1,2-dimethoxypropane, 1,2-dimethoxyethane,2-butanone, 2-pentanone, 3-pentanone, methyl isobutyl ketone, ethylisobutyl ketone, methyl isopropyl ketone, cyclopentanone, cyclohexanone,acetophenone, isophorone, mesityl oxide, benzene, toluene, xylene, ethylbenzene, chlorobenzene, 1,2-dichlorobenzene, α,α,α-trifluorotoluene,pentane, hexane, heptane, octane, cyclohexane, methylcyclohexane,cyclohexene, and mixtures thereof.

Depending on the solubility characteristics of the PI or PAE polymer,the purification solvent(s) may be used as the sole solvent(s) in thedilution/purification step. However, in some embodiments, in addition tothe purification solvent(s), a purification co-solvent(s) may beemployed. Purification co-solvents are organic solvents that have ahigher (e.g., significantly higher) solubility in water at 25° C. thanthe purification solvent(s). In general, a purification co-solvent(s) isnot used alone but is used in combination with one or more purificationsolvent(s). In some embodiments, the purification solvents can be waterimmiscible solvents.

Examples of suitable purification co-solvents include, but are notlimited to, acetone, gamma-butyrolactone (GBL), furan, tetrahydrofuran,methyl tetrahydrofuran, tetrahydrofurfuryl methyl ether, 1,4-dioxane,and mixtures thereof. In some embodiments, the purification co-solventscan be water miscible solvents.

Step 3—Washing the Diluted Organic Solution

Once the PI or PAE polymer has been diluted in the purificationsolvent(s), this diluted organic solution can be subjected to washingwith water and/or an aqueous solution containing an additive (e.g., anacid or a base) to obtain a washed organic solution. Without wishing tobe bound by theory, it is believed that this step can purify the PI orPAE polymer by removal of the polymerization solvent(s), polymerizationby-products, catalysts, residual monomers and other impurities from thepolymer-containing organic phase into the aqueous phase.

When an aqueous solution containing an additive is employed in thisstep, this solution can contain an acid, a base, or additionalcomponents, such as chelating agents, in a sufficient concentration toenhance the purity of the PI or PAE polymer by removal of impurities(e.g., polymerization by-products). The concentration of the acid, thebase, or other additives in this aqueous solution may range from atleast about 0.1 wt % (e.g. at least about 0.3 wt %, at least about 0.5wt %, or at least about 1 wt %) to at most about 10 wt % (e.g. at mostabout 8 wt %, at most about 7 wt %, or at most about 5 wt %).

In some embodiments, the washing step can include adding water or anaqueous solution to the diluted organic solution obtained in thedilution step above. In such embodiments, the washing step can includeforming a mixture having an organic phase and an aqueous phase (e.g., byallowing the organic phase and the aqueous phase to separate from eachother). The washing step can further include removing the aqueous phase.In general, washing the diluted solution can substantially remove the atleast one polymerization solvent or another impurity in the dilutedorganic solution.

In order to improve the effectiveness of the washing step, the dilutedorganic solution from step 2 containing a PI or PAE polymer and theaqueous washing medium (e.g., water or an aqueous solution) can be mixedby agitation. This agitation may take the form of stirring, shaking,inverting or any other method which permits effective mixing of theorganic and aqueous phases.

Following mixing, the mixture can be allowed to stand undisturbed untiltwo distinct and separate phases are formed. Upon the formation ofdistinct and separate phases, the aqueous phase can be removed anddiscarded to remove impurities (e.g., a polymerization solvent). Step 3(and optionally together with step 2, as required) may be repeated anynumber of times to achieve the desired polymer purity. In someembodiments, the number of aqueous washes is from one to five (i.e.,one, two, three, four or five).

The total amount of water and/or aqueous solution containing an additiveemployed to purify the PI or PAE polymer ranges from about one kilogramto about 80 kilograms of aqueous medium per kilogram of polymer.

A wide range of agitation rate, time, temperature and separationconditions may be employed. Without wishing to be bound by theory, it isbelieved that an essential aspect of this step is to ensure sufficientmixing of the mixtures to extract significant amounts of thepolymerization solvent(s) and other impurities into the aqueous phasefollowed by phase separation. These conditions may vary depending on thevessel employed for the mixing and separation. In some embodiments, theagitation time is from about 1 minute to about 24 hours (e.g., fromabout 10 minutes to about 6 hours). In some embodiments, the agitationtemperature is from about 10° C. to about 40° C. (e.g., from about 15°C. to about 30° C.). In some embodiments, the separation time is fromabout 10 minutes to about 24 hours (e.g., from about 15 minutes to about12 hours). In some embodiments, the separation temperature is from about10° C. to about 40° C. (e.g., from about 15° C. to about 30° C.).

In some embodiments, when a PI polymer is being formed and purified, theamount of residual polymerization solvent(s) remaining after the finalaqueous washing is at most about 1 wt % (e.g., at most about 0.5 wt %)of the weight of the PI polymer. In some embodiments, when a PAE polymeris being formed and purified, the amount of residual polymerizationsolvent(s) remaining after the final aqueous washing is at most about 5wt % (e.g., at most about 4 wt %, at most about 3 wt %, at most about 2wt %, at most about 1 wt %, at most about 0.5 wt %) of the weight of thePAE polymer.

Step 4—Solvent Removal and/or Exchange

After the organic solution containing a PI or PAE polymer is washed byan aqueous medium (e.g., water), at least a portion (e.g., substantiallyall) of the purification solvent(s) in the organic solution can beremoved or exchanged for at least one isolation solvent(s) to obtain asolution containing a purified PI or PAE polymer (i.e., a purifiedpolymer solution).

In some embodiments, at least a portion (e.g., substantially all) of thepurification solvent(s) (and essentially all residual water) in thepurified polymer solution can be solvent exchanged for an isolationsolvent(s). In some embodiments, the isolation solvent(s) is a solventor combination of two or more solvents whose boiling point is equal toor greater than the purification solvent(s). In certain embodiments, theisolation solvent(s) can be the same as the purification solvent(s) orpolymerization solvent(s). In other embodiments, the isolationsolvent(s) can be different from the purification solvent(s) orpolymerization solvent(s). In some embodiments, the isolation solvent(s)are compatible with various coating and application methods employed inmany industrial applications.

In some embodiments, the isolation solvent(s) can include a ketone, anester, a hydrocarbon, a sulfoxide, an ether, or a mixture thereof.Examples of suitable isolation solvent(s) include, but are not limitedto, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK),2-heptanone, cyclopentanone, cyclohexanone, xylene, gamma-butyrolactone,dimethylsulfoxide, propylene glycol monomethyl ether acetate (PGMEA),propylene glycol monomethyl ether (PGME), ethyl lactate (EL) andmixtures thereof.

In some embodiments, the isolation solvent(s) can be first added to thewashed, purified organic solution containing a PI or PAE polymer. Insuch embodiments, the purification solvent(s) can then be removed byevaporation or distillation. In some embodiments, the amount of residualpurification solvent(s) remaining after this step can be at most about 2wt % (e.g., at most about 1 wt %) of the weight of the PI or PAEpolymer. Without wishing to be bound by theory, it is believed thatadding an isolation solvent(s) have a boiling point higher than that ofthe purification solvent(s) can facilitate the removal of thepurification solvent(s) during distillation.

Without wishing to be bound by theory, it is believed that, in additionto exchanging the purification solvent(s) for the isolation solvent(s),this step also serves to dry the final polymer solution by removingresidual water along with the purification solvent(s) (e.g., throughdistillation).

In some embodiments, after at least a portion (e.g., substantially all)of the purification solvent(s) is exchanged for the isolationsolvent(s), the solution containing the PI or PAE polymer can beconcentrated to form a solution suitable for coating on a substrate.

In some embodiments, when the isolation solvent(s) is the same as thepurification solvent(s), the solvent removal step can be performed byfirst adding a certain amount of purification solvent(s) into thewashed, purified organic solution containing a PI or PAE polymer. Atleast a portion of the purification solvent(s) in the solution thusformed can then be removed (e.g., by evaporation or distillation).Without wishing to be bound by theory, it is believed that this processcan improve the purity of the final polymer solution by removal ofresidual water and polymerization solvent(s) with the purificationsolvent(s) (e.g., by evaporation or distillation). Further, withoutwishing to be bound by theory, it is believed that adding thepurification solvent(s) in this step can prevent the polymer fromprecipitation out of the solution during the solvent removal process.

The distillation conditions can be any temperature and pressure underwhich the polymer is stable that will produce the desired end result. Insome embodiments, the distillation temperature is from about 20° C. toabout 70° C. (e.g., from about 25° C. to about 45° C.). In someembodiments, the distillation pressure is from about 760 Torr to about0.1 Torr (e.g., from about 100 Torr to about 0.1 Torr). While theprocess detailed above leads to PI and PAE polymers of enhanced purity,it should be noted that additional process steps including, but notlimited to, ion exchange and filtration may be included before and/orafter steps 3 and 4 in this process.

In some embodiments, this disclosure features a purified PI or PAEpolymer solution obtained from the process above. In some embodiments, apurified PI or PAE polymer can be isolated from the purified polymersolution obtained above by any suitable method known in the art (e.g.,by precipitation or removal of solvents via distillation).

In one embodiment, the PI and PAE polymers of enhanced purity producedusing the process of the present disclosure can be incorporated intocompositions (e.g., film-forming compositions, thermally curablecompositions, photosensitive compositions).

In some embodiments, this disclosure features a process of preparing afilm on a substrate (e.g., a semiconductor substrate). The process caninclude (a) providing an organic solution containing a polyimide orpolyamic ester in at least one polar, aprotic polymerization solvent;(b) adding at least one purification solvent to the organic solution toform a diluted organic solution, the at least one purification solventis less polar than the at least one polymerization solvent and has alower water solubility than the at least one polymerization solvent at25° C.; (c) washing the diluted organic solution with water or anaqueous solution to obtain a washed organic solution; (d) removing atleast a portion of the at least one purification solvent in the washedorganic solution to obtain a solution containing a purified polyimide orpolyamic ester; and (e) coating the solution containing a purifiedpolyimide or polyamic ester on a substrate to form a film.

In some embodiments, the coating step described above can be performedby ink jet printing, spin coating, spray coating, dip coating, rollercoating, or dynamic surface tension coating.

In some embodiments, this disclosure features an article that includes asemiconductor substrate and a film formed by the process above on thesemiconductor substrate. Examples of such articles include a wireisolation, a wire coating, a wire enamel, or an inked substrate. In someembodiments, this disclosure features a semiconductor device containingthe article described above. For example, the semiconductor device canbe an integrated circuit, a light emitting diode, a solar cell, and atransistor.

In some embodiments, this disclosure is directed to a process forproducing a free-standing film from the purified PI or PAE polymersolutions described herein, as well as the free-standing film thusobtained. The process can include the following steps:

-   -   a) coating a substrate with a purified PI or PAE polymer        solution described herein to form a film coated substrate,    -   b) baking the film coated substrate (e.g., in a first baking        step at a temperature T₁) to remove at least a portion (e.g.,        substantially all) of the solvent in the purified PI or PAE        polymer solution; and    -   c) releasing the film coating from the substrate (e.g., by        applying a mechanical force or a chemical treatment) to obtain a        free-standing film.        In some embodiments, T₁ can be less than about 150° C. Examples        of suitable substrates that can be used in the above process        include, but not limited to, semiconductor substrates such as a        silicon oxide wafer (which can facilitate release of the film by        using a HF treatment), various plastic carriers such as        polyethylene terephthalate (PET) substrates (which is flexible        and can be easily removed by peeling), ceramic, glass panel or        flexible glass film, textiles films, metal foil or sheet (such        as copper or aluminum sheet), paper and the like.

Optionally, additional treatment of the film, such as exposure toradiation, corona, plasma and/or microwave radiation or a second bakingstep at a temperature T₂ (e.g., from about 180° C. to about 250° C.) canbe applied to cure the film coating after the first baking step andbefore releasing the film to become free-standing.

Optionally, additional treatments that can be applied to thefree-standing film include, but not limited to, washing thefree-standing film with water or solvent and/or drying the free-standingfilm.

An example of the mechanical force to remove the film includes, but notlimited to, peeling. An example of a chemical treatment to release thefilm includes, but not limited to, a dilute aqueous HF solutiontreatment.

In some embodiments, once the free-standing film is formed, it can beapplied to a semiconductor substrate suitable for use in semiconductordevices. Examples of such semiconductor substrates include printedcircuit boards and flexible printed circuit boards.

The contents of all publications cited herein (e.g., patents, patentapplication publications, and articles) are hereby incorporated byreference in their entirety.

EXAMPLES Abbreviation

6FDA: 2,2′-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydrideDAPI: 4,4′-[1,4-phenylene-bis(1-methylethylidene)]bisanilineBTDA: 3,3′,4,4′-benzophenone tetracarboxylic dianhydridePMDA: Pyromellitic dianhydrideODA: 4,4′-oxydianiline ODPA: 4,4′-oxydiphthalic anhydrideDAM: 1,3-diaminomesitylene

HEMA: Hydroxyethylmethacrylate

NMP: N-Methyl pyrrolidinone

GBL: Gamma-butyrolactone DMSO: Dimethylsulfoxide Example 1

An example of a PI polymer was prepared using one diamine and onedianhydride where the isolation solvent (i.e., a lactone) was differentfrom the purification solvents (i.e., an ester and a ketone). The ratioof water to polymer used was 46:1.

Solid 6FDA (334.0 g) was charged to a solution of DAPI (218.4 g) in NMP(2206 g) at room temperature. Additional NMP (816 g) was used to rinsethe dianhydride into solution. The reaction temperature was increased to60° C. and the mixture was allowed to react for 3.5 hours. Next, aceticanhydride (125.7 g) and pyridine (49.5 g) were added, the reactiontemperature was increased to 100° C., and the mixture was allowed toreact for 12 hours.

The reaction mixture was cooled to room temperature and transferred to alarger vessel equipped with a mechanical stirrer. The reaction solutionwas diluted using ethyl acetate as a purification solvent and washedwith water for one hour. Stirring was stopped and the mixture wasallowed to stand undisturbed. Once phase separation had occurred, theaqueous phase was removed. The organic phase was diluted using acombination of ethyl acetate and acetone as purification solvents andwashed three more times with water. The amounts of purification solvents(i.e., ethyl acetate and acetone) and water used in all of the washesare shown in Table 1.

TABLE 1 Wash 1 Wash 2 Wash 3 Wash 4 Ethyl Acetate (g) 4085 1897 10251030 Acetone (g) — 696 570 570 Water (g) 5311 6585 6580 6700

The washed organic phase was concentrated by vacuum distillation. GBL(705 g) was added as an isolation solvent and vacuum distillation wascontinued. The final polymer solution had a concentration of 33.82 wt %.Upon GC analysis, there was no detectable NMP in the final polymersolution.

Example 2

An example of an end-capped PI polymer was prepared using one diamineand one dianhydride where the isolation solvent (i.e., a lactone) wasdifferent from the purification solvents (i.e., an ester and a ketone).The ratio of the aqueous washing solution to polymer used was 48:1.

Solid 6FDA (244.3 g) was charged to a solution of DAPI (159.8 g) in NMP(2290 g) at room temperature. The reaction temperature was increased to60° C. and the mixture was allowed to react for 3 hours. Next,7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic anhydride (16.7 g) wasadded to the reaction mixture. After an additional 3 hours at 60° C.,acetic anhydride (92.0 g) and pyridine (36.2 g) were added, the reactiontemperature was increased to 100° C., and the mixture was allowed toreact for 12 hours.

The reaction mixture was cooled to room temperature and transferred to alarger vessel equipped with a mechanical stirrer. The reaction solutionwas diluted using ethyl acetate as a purification solvent and washedwith a 1% solution of aqueous hydrochloric acid for one hour. Stirringwas stopped and the mixture was allowed to stand undisturbed. Once phaseseparation had occurred, the aqueous phase was removed. The organicphase was diluted using a combination of ethyl acetate and acetone aspurification solvents and washed three times with water. The amounts ofpurification solvents (i.e., ethyl acetate and acetone) and water usedin all of the washes are shown in Table 2.

TABLE 2 Wash 1 Wash 2 Wash 3 Wash 4 Ethyl Acetate (g) 3111 1447 778 780Acetone (g) — 527 429 440 1% Aqueous HCl (g) 4045 — — — Water (g) — 50155009 5014

The washed organic phase was concentrated by vacuum distillation. GBLwas added as an isolation solvent and vacuum distillation was continued.The final polymer solution had a concentration of 41.99 wt %. Upon GCanalysis, there was no detectable NMP in the final polymer solution.

Example 3

An example of an end-capped PI polymer was prepared using one diamineand one dianhydride where the isolation solvent (i.e., a lactone) wasdifferent from the purification solvents (i.e., an ester and a ketone).The ratio of water to polymer used was 48:1.

Solid 6FDA (333.9 g) was charged to a solution of DAPI (218.4 g) in NMP(2721 g) at room temperature. Additional NMP (410 g) was used to rinsethe dianhydride into solution. The reaction temperature was increased to60° C. and the mixture was allowed to react for 5 hours. Next,7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic anhydride (22.8 g) andNMP (21.8 g) were added to the reaction mixture. After an additional 3hours at 60° C., acetic anhydride (126.6 g) and pyridine (48.9 g) wereadded, the reaction temperature was increased to 100° C., and themixture was allowed to react for 12 hours.

The reaction mixture was cooled to room temperature and transferred to alarger vessel equipped with a mechanical stirrer. The reaction solutionwas diluted with ethyl acetate as a purification solvent and washed withwater for one hour. Stirring was stopped and the mixture was allowed tostand undisturbed. Once phase separation had occurred, the aqueous phasewas removed. The organic phase was diluted with a combination of ethylacetate and acetone as purification solvents and washed three more timeswith water. The amounts of purification solvents (i.e., ethyl acetateand acetone) and water used in all of the washes are shown in Table 3.

TABLE 3 Wash 1 Wash 2 Wash 3 Wash 4 Ethyl Acetate (g) 4237 1967 10611057 Acetone (g) — 724 586 589 Water (g) 5508 6820 6817 6822

The washed organic phase was concentrated by vacuum distillation. GBL(706 g) was added as an isolation solvent and vacuum distillation wascontinued. The final polymer solution had a concentration of 43.75 wt %.The NMP content of the final polymer solution was determined by GC to be0.05 wt % of the polymer.

Example 4

An example of an end-capped PI polymer was prepared using two diaminesand one dianhydride where the isolation solvent (i.e., a ketone) was thesame as one of the purification solvents (i.e., a ketone and an aromatichydrocarbon). The ratio of water to polymer used was 21:1.

A solution of DAPI (160 g) and DAM (90.2 g) in NMP (667 g) was addedslowly by addition pump to a slurry of BTDA (367.3 g) in NMP (772.8 g)at 50° C. When addition was complete, the reaction temperature wasincreased to 60° C. and the mixture was allowed to react for 18 hours.Next, solid 5-isobenzofurancarboxylic acid,1,3-dihydro-1,3-dioxo-2-[(2-methyl-1-oxo-2-propen-1-yl)oxy]ethyl ester(36.6 g) and NMP (205 g) were added to the reaction mixture. After anadditional 6 hours at 60° C., pyridine (47.7 g) and NMP (180 g) wereadded. After an additional 18 hours at 60° C., acetic anhydride (122.4g) was added, the reaction temperature was increased to 100° C., and themixture was allowed to react for 12 hours.

The reaction mixture was cooled to room temperature and 303.5 g of themixture was transferred to a separatory flask equipped with a mechanicalstirrer. The reaction solution was diluted with cyclopentanone andtoluene as purification solvents and washed with water for one hour.Stirring was stopped and the mixture was allowed to stand undisturbed.Once phase separation had occurred, the aqueous phase was removed. Theorganic phase was diluted with cyclopentanone as a purification solventand washed three more times with water. The amounts of purificationsolvents (i.e., cyclopentanone and toluene) and water used in all of thewashes are shown in Table 4.

TABLE 4 Wash 1 Wash 2 Wash 3 Wash 4 Toluene (g) 306.3 — — —Cyclopentanone (g) 599.3 124.5 99.3 102.8 Water (g) 605.0 401.6 403.7402.1

The washed organic phase was concentrated by vacuum distillation.Cyclopentanone (300.6 g) was added as an isolation solvent and vacuumdistillation was continued. The final polymer solution had aconcentration of 33.92 wt %. The NMP content of the final polymersolution was determined by GC to be 0.29 wt % of the polymer.

Example 5

An example of an end-capped PI polymer was prepared using two diaminesand two dianhydrides where the isolation solvent (i.e., a ketone) wasthe same as one of the purification solvents (i.e., a ketone and anaromatic hydrocarbon). The ratio of water to polymer used was 20:1.

A solution of DAPI (199.8 g) and DAM (112.7 g) in NMP (574 g) was addedslowly by addition pump to a slurry of BTDA (221.5 g) and PMDA (150.0 g)in NMP (1022.5 g) at room temperature. When addition was complete,additional NMP (455 g) was added, the reaction temperature was increasedto 60° C., and the mixture was allowed to react for 18 hours. Next,solid 5-isobenzofurancarboxylic acid,1,3-dihydro-1,3-dioxo-2-[(2-methyl-1-oxo-2-propen-1-yl)oxy]ethyl ester(76.1 g) and NMP (59 g) were added to the reaction mixture. After anadditional 20 hours at 60° C., acetic anhydride (153.4 g) and pyridine(60.1 g) were added, the reaction temperature was increased to 100° C.,and the mixture was allowed to react for 15 hours.

The reaction mixture was cooled to room temperature and 414.4 g of themixture was transferred to a separatory flask equipped with a mechanicalstirrer. The reaction solution was diluted using cyclopentanone andtoluene as purification solvents and washed with water for one hour.Stirring was stopped and the mixture was allowed to stand undisturbed.Once phase separation had occurred, the aqueous phase was removed. Theorganic phase was diluted with cyclopentanone as a purification solventand washed three more times with water. The amounts of purificationsolvents (i.e., cyclopentanone and toluene) and water used in all of thewashes are shown in Table 5.

TABLE 5 Wash 1 Wash 2 Wash 3 Wash 4 Toluene (g) 410.5 — — —Cyclopentanone (g) 639.5 90.7 99.4 100.2 Water (g) 612.1 600.9 402.5400.8

The washed organic phase was concentrated by vacuum distillation.Cyclopentanone (378.5 g) was added as an isolation solvent and vacuumdistillation was continued. The final polymer solution had aconcentration of 31.23 wt %. The NMP content of the final polymersolution was determined by GC to be 0.40 wt % of the polymer.

Example 6

An example of a non-end-capped PI polymer was prepared using one diamineand one dianhydride where the isolation solvent (i.e., a lactone) wasdifferent from the purification solvents (i.e., an ester and a ketone).The ratio of water to polymer used was 46:1.

Solid 6FDA (81.52 g) was charged to a solution of ODA (40.10 g) in NMP(539.7 g) at room temperature. Additional NMP (146 g) was used to rinsethe dianhydride into solution. The reaction temperature was increased to60° C. and the mixture was allowed to react for 4 hours. Next, aceticanhydride (32.32 g) and pyridine (12.00 g) were added, the reactiontemperature was increased to 100° C., and the mixture was allowed toreact for 12 hours.

The reaction mixture was cooled to room temperature and 96.1 g wastransferred to a separatory funnel. The reaction solution was dilutedusing cyclopentanone and toluene as purification solvents and washedwith water by inverting the funnel twenty times. The mixture was allowedto stand undisturbed until two separate and distinct layers were formed.Once phase separation had occurred, the aqueous phase was removed. Theorganic phase was diluted using cyclopentanone as a purification solventand washed four more times with water. The amounts of purificationsolvents (i.e., cyclopentanone and toluene) and water used in all of thewashes are shown in Table 6.

TABLE 6 Wash 1 Wash 2 Wash 3 Wash 4 Wash 5 Toluene (g) 96.5 — — — —Cyclopentanone (g) 99.6 65.2 43.3 44.7 25.9 Water (g) 177.0 175.1 154.7161.8 140.5

A portion of the washed organic phase was concentrated by vacuumdistillation. Cyclopentanone (179.7 g) was added as an isolation solventand vacuum distillation was continued. The final polymer solution had aconcentration of 8.86 wt %. Upon GC analysis, there was no detectableNMP in the final polymer solution.

The reagents used and the properties of the polymers obtained inExamples 1-6 are summarized in Table 7.

TABLE 7 SOLUBLE POLYIMIDE POLYMER DATA Polymer Example 1 Example 2Example 3 Example 4 Example 5 Example 6 Diamine(s) DAPI DAPI DAPIDAPI:DAM DAPI:DAM ODA Dianhydride(s) 6FDA 6FDA 6FDA BTDA BTDA:PMDA 6FDAMolecular Weight 14900 25000 24000 25700 13100 15400 PDI 2.3 2.8 2.8 2.82.5 2.2 Solids (Wt %) 33.82 41.99 43.75 33.92 31.23 NMP Content (Wt %)ND ND 0.05 0.29 0.4 ND ND: Not detectable.

Example 7

An example of a PAE polymer was prepared using one diamine and onedianhydride where the isolation solvents (i.e., a lactone and asulfoxide) were different from the purification solvents (i.e., an esterand a ketone). The ratio of water to polymer used was 69:1.

In a 5-L jacketed vessel, HEMA (108.72 g) was added to a slurry of ODPA(126.65 g), hydroquinone (0.22 g) and pyridine (143.56 g) in diglyme(691 g) at room temperature. The reaction mixture was heated to 70° C.for 4 hours and then cooled to −10° C. A solution of thionyl chloride(100.97 g) in diglyme (369 g) was slowly added to the reaction mixtureat −10° C. The reaction mixture was warmed to 0° C. for 1 hour and thenre-cooled to −10° C. NMP (312 g) was added to the reaction mixturefollowed by slow addition of a solution of ODA (483.23 g) in NMP (74.4g). Following addition of ODA, the reaction mixture was warmed to 0° C.for 30 minutes and then warmed to 10° C. Anhydrous ethanol (452.5 g) wasadded and the reaction mixture warmed to room temperature.

A portion of the reaction mixture (523.2 g) was transferred to aseparatory flask equipped with a mechanical stirrer. The reactionsolution was diluted with cyclopentanone and ethyl acetate aspurification solvents and washed with water for one hour. Stirring wasstopped and the mixture was allowed to stand undisturbed. Once phaseseparation had occurred, the aqueous phase was removed. The organicphase was diluted with cyclopentanone as a purification solvent andwashed three more times with water. The amounts of purification solvents(i.e., cyclopentanone and ethyl acetate) and water used in all of thewashes are shown in Table 8.

TABLE 8 Wash 1 Wash 2 Wash 3 Wash 4 Ethyl Acetate (g) 520.4 — — —Cyclopentanone (g) 237.2 154.0 162.3 168.0 Water (g) 877.3 876.0 877.7880.5

The washed organic phase was concentrated by vacuum distillation. A80:20 mixture of GBL:DMSO (59.4 g) was added as isolation solvents andvacuum distillation was continued. The final polymer solution had aconcentration of 44.68 wt %.

The NMP content of the purified polymer was determined by GC to be 4.29wt % of the polymer. Although the process described in Example 7 forpurifying a PAE polymer has not been optimized, the above results showthat it can reduce the residual amount of the polymerization solvent(i.e., NMP) to a level much lower than that obtained by ComparativeExample 1 (i.e., 6.15 wt %), which describes a conventionalprecipitation method for purifying the same PAE polymer.

Comparative Example 1

A portion of the reaction mixture produced in Example 7 was purified bya conventional method as follows. The ratio of water to polymer used was492:1.

The PAE polymerization solution (2997 g) was slowly added to water (36.0kg) to precipitate the crude polymer. The crude polymer was isolated byvacuum filtration, washed with water (28.8 kg) and dried under vacuum.The crude dry polymer (131 g) was dissolved in THF (750 g) in a glassbottle, water (80 g) was added and the solution mixed by rolling for 1hour. UP6040 ion exchange resin (131 g) was added, and the mixturerolled overnight. The mixture was filtered to remove ion exchange resinand the filtrate was slowly added to water (12.0 kg) to re-precipitatethe polymer. The solid polymer was collected by vacuum filtration,washed with water (9.6 kg) and dried under vacuum at 45° C. overnight.The NMP content of the final precipitated polymer was determined by GCto be 6.15 wt % of the polymer.

GPC analysis of the final solid polymer produced by the conventionmethod with the polymer solution produced in Example 7 are provided inFIG. 1, which shows that the molecular weight profiles of the polymerswere identical. Table 9 summarizes the differences between the processesused and the polymers obtained in Example 7 and Comparative Example 1.

TABLE 9 PROCESS COMPARISON: EXAMPLE 7 AND COMPARATIVE EXAMPLE 1Comparative Example Example Example 1 7 Unit Molecular 31200 31900Daltons Weight PDI 2.4 2.4 Water Used 492 69 kg/kg of Polymer IEX NeededYes No

As shown in Table 9, the process described in Example 7 cansignificantly reduce the amount of water used and thereby generatesignificantly less waste compared to the conventional precipitationprocess described in Comparative Example 1.

Comparative Example 2

A portion of the reaction mixture produced in Example 4 was purified bya conventional method as follows.

A portion of the PI polymerization solution (100 g) was diluted with anequal volume of THF and the diluted solution was slowly added to water(2000 g) to precipitate the crude polymer. The crude polymer wasisolated by vacuum filtration and washed with water. The crude wetpolymer was slurried with methanol, collected by vacuum filtration anddried under vacuum at 45° C. overnight.

The NMP content of the final precipitated polymer was determined by GCto be 2.25 wt % of the polymer.

Comparative Example 3

A portion of the reaction mixture produced in Example 6 was purified bya conventional method as follows.

A portion of the PI polymerization solution (10 g) was diluted with anequal volume of THF and the diluted solution was slowly added to water(200 g) to precipitate the crude polymer. The crude polymer was isolatedby vacuum filtration and washed with water. The crude wet polymer wasslurried with methanol, collected by vacuum filtration and dried undervacuum at 45° C. overnight.

The NMP content of the final precipitated polymer was determined by GCto be 6.08 wt % of the polymer.

Composition and Film Example 1 A Film Forming Composition

A mixture containing 100 parts of the polymer solution obtained inExample 1 and 1.5 part of (3-triethoxysilyl)propyl succinic anhydrideare prepared and filtered by using a 1.0 micron filter. The compositionis spin coated on a silicon wafer to form a coating with a thickness of10 microns. The coated wafer is baked at 120° C. for 3 minutes. Coatingdefects and film cracking are checked by optical microscope.

Composition and Film Example 2 A Film Forming, Thermally-CurableComposition

A thermosetting composition is prepared by mixing 100 parts of thepolymer solution obtained in Example 2, 8.5 parts of dipentaerythritolhexakis (3-mercaptopropionate), 0.5 parts of N-methyldicyclohexyl amine,and 4.5 part of gamma-glycidoxypropyltriethoxysilane. The composition isfiltered by using a 1.0 micron filter. The composition is spin coated ona silicon wafer to form a coating with a thickness of 10 microns. Thecoated wafer is baked at 125° C. for 5 minutes. Coating defects and filmcracking are checked by optical microscope. The film is heated under N₂atmosphere in a convection oven at 200° C. for 1 hour. The resultingfilm is again checked by optical microscope for film defects. The filmis immersed in various solvents (PGMEA, GBL, and acetone) to evaluateits solvent resistance.

Composition and Film Example 3 A Film Forming, Thermally-CurableComposition

A thermosetting composition is prepared by mixing 100 parts of thepolymer solution obtained in Example 3, 7 parts of trimethylolpropanetris(4-sulfanylcyclohexanecarboxylate), 0.7 parts of triethylamine, and3 part of (3-triethoxysilylpropyl)-t-butyl carbamate. The composition isfiltered by using a 1.0 micron filter. The composition is spin coated ona silicon wafer to form a coating with a thickness of 12 microns. Thecoated wafer is baked at 130° C. for 4 minutes. Coating defects and filmcracking are checked by optical microscope. The film is heated under N₂atmosphere in a convection oven at 220° C. for 1 hour. The resultingfilm is checked again by optical microscope for film defects. The filmis immersed in various solvents (PGMEA, GBL, and acetone) to evaluateits solvent resistance.

Composition and Film Example 4 A Film Forming, PhotosensitiveComposition

A photosensitive composition is prepared by mixing 100 parts of thepolymer solution obtained in Example 4, 20 parts of tetraethyleneglycoldimethacrylate and 1.5 parts of NCI-831 (trade name, available fromADEKA Corporation). The composition is filtered by using a 0.2 micronfilter and is spin coated on a silicon wafer to form a coating with athickness of about 9 microns. The coated wafer is baked at 105° C. for 3minutes. The photosensitive polyimide film is exposed with a broadbandUV exposure tool (Carl Süss MA-56) through a mask having a desiredpattern for exposure.

After the exposure, unexposed portions are removed by usingcyclopentanone as developer followed by rinsing the developed film withPGMEA to form a pattern. After pattern formation, the developed film isheated at a temperature of 100° C. for a time period of 2 minutes. Theresulting film is checked by optical microscope for film defects.

What is claimed is:
 1. A process of purifying a polymer, comprising:providing an organic solution containing a polyimide or polyamic esterin at least one polar, aprotic polymerization solvent; adding at leastone purification solvent to the organic solution to form a dilutedorganic solution, the at least one purification solvent is less polarthan the at least one polymerization solvent and has a lower watersolubility than the at least one polymerization solvent at 25° C.;washing the diluted organic solution with water or an aqueous solutionto obtain a washed organic solution; and removing at least a portion ofthe at least one purification solvent in the washed organic solution toobtain a solution containing a purified polyimide or polyamic ester. 2.The process of claim 1, wherein the at least one polymerization solventcomprises dimethylformamide, dimethylacetamide, N-formylmorpholine,N-methylpyrrolidinone, N-ethylpyrrolidinone, dimethylsulfoxide,gamma-butyrolactone, hexamethyl phosphoric acid triamide,tetrahydrofuran, methyltetrahydrofuran, 1,4-dioxane, or a mixturethereof.
 3. The process of claim 1, wherein the at least onepolymerization solvent comprises at least one water miscible solvent. 4.The process of claim 1, wherein the at least one purification solventcomprises an ester, an ether, a ketone, a hydrocarbon optionallysubstituted by at least one halide, or a mixture thereof.
 5. The processof claim 4, wherein the least one purification solvent comprises methylacetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butylacetate, isobutyl acetate, sec-butyl acetate, cyclohexyl acetate, ethyllactate, propylene glycol monomethyl ether acetate, tetrahydrofurfurylacetate, propyl formate, butyl formate, isobutyl formate, pentylformate, ε-caprolactone, diethyl ether, dipropyl ether, dibutyl ether,dicyclohexyl ether, cyclopentyl methyl ether, methyl tert-butyl ether,ethyl tert-butyl ether, anisole, phenyl ethyl ether, diphenyl ether,1,2-dimethoxypropane, 1,2-dimethoxyethane, 2-butanone, 2-pentanone,3-pentanone, methyl isobutyl ketone, ethyl isobutyl ketone, methylisopropyl ketone, cyclopentanone, cyclohexanone, acetophenone,isophorone, mesityl oxide, benzene, toluene, xylene, ethyl benzene,chlorobenzene, 1,2-dichlorobenzene, α,α,α-trifluorotoluene, pentane,hexane, heptane, octane, cyclohexane, methylcyclohexane, cyclohexene, ora mixture thereof.
 6. The process of claim 1, wherein the least onepurification solvent comprises at least one water immiscible solvent. 7.The process of claim 1, wherein adding at least one purification solventfurther comprises adding at least one purification co-solvent that has awater solubility higher than the at least one purification solvent. 8.The process of claim 7, wherein the at least one purification co-solventcomprises acetone, gamma-butyrolactone, furan, tetrahydrofuran, methyltetrahydrofuran, tetrahydrofurfuryl methyl ether, 1,4-dioxane, or amixture thereof.
 9. The process of claim 8, wherein the at least onepurification co-solvent comprises at least one water miscible solvent.10. The process of claim 1, wherein the aqueous solution comprises anadditive.
 11. The process of claim 1, wherein washing the dilutedorganic solution comprises adding water or an aqueous solution to thediluted organic solution.
 12. The process of claim 11, wherein washingthe diluted organic solution further comprises forming a mixture havingan organic phase and an aqueous phase.
 13. The process of claim 12,wherein washing the diluted organic solution further comprises removingthe aqueous phase.
 14. The process of claim 1, wherein washing thediluted solution substantially removes the at least one polymerizationsolvent or another impurity in the diluted organic solution.
 15. Theprocess of claim 1, wherein the removing step comprises adding at leastone isolation solvent to the washed organic solution.
 16. The process ofclaim 15, wherein the at least one isolation solvent has a boiling pointhigher than a boiling point of the at least one purification solvent.17. The process of claim 15, wherein the at least one isolation solventcomprises a ketone, an ester, a hydrocarbon, a sulfoxide, an ether, or amixture thereof.
 18. The process of claim 17, wherein the at least oneisolation solvent comprises methyl ethyl ketone, methyl isobutyl ketone,2-heptanone, cyclopentanone, cyclohexanone, xylene, gamma-butyrolactone,dimethylsulfoxide, propylene glycol monomethyl ether acetate, propyleneglycol monomethyl ether, ethyl lactate, or a mixture thereof.
 19. Theprocess of claim 15, wherein the at least one isolation solvent isdifferent from the at least one purification solvent.
 20. The process ofclaim 15, wherein the at least one isolation solvent is the same as theat least one purification solvent.
 21. The process of claim 1, whereinthe at least a portion of the at least one purification solvent isremoved by evaporation or distillation.
 22. The process of claim 1,wherein the organic solution containing a polyimide or polyamic ester inat least one polar, aprotic polymerization solvent is obtained from apolymerization reaction without isolating the polyimide or polyamicester.
 23. The process of claim 1, further comprising concentrating thesolution containing a purified polyimide or polyamic ester after theremoving step.
 24. A purified polymer obtained by the process ofclaim
 1. 25. A process of preparing a film on a substrate, comprising:providing an organic solution containing a polyimide or polyamic esterin at least one polar, aprotic polymerization solvent; adding at leastone purification solvent to the organic solution to form a dilutedorganic solution, the at least one purification solvent is less polarthan the at least one polymerization solvent and has a lower watersolubility than the at least one polymerization solvent at 25° C.;washing the diluted organic solution with water or an aqueous solutionto obtain a washed organic solution; removing at least a portion of theat least one purification solvent in the washed organic solution toobtain a solution containing a purified polyimide or polyamic ester; andcoating the solution containing a purified polyimide or polyamic esteron a substrate to form a film.
 26. The process of claim 25, wherein theremoving step comprises adding at least one isolation solvent to thewashed organic solution.
 27. The process of claim 25, wherein thecoating step is performed by ink jet printing, spin coating, spraycoating, dip coating, roller coating, or dynamic surface tensioncoating.
 28. The process of claim 25, further comprising removing thefilm from the substrate.
 29. A free-standing film obtained by theprocess of claim
 28. 30. An article, comprising a semiconductorsubstrate and a film prepared by the process of claim 25 on thesemiconductor substrate.